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  <meta charset="UTF-8">
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  <title>Document</title>
</head>
<body>
  <script>
    // 简单数据类型  栈  number string undefeind boolean null

    // 复杂数据类型  堆  array  obj  date Math


    // var num = 123
    // var count = num
    // count = 456

    // console.log(num)  // 123
    // console.log(count)  // 456


    var arr = [1, 2]

    var arr2 = arr
    arr2.push(3)


    console.log(arr)  // [1,2,3]


  </script>
</body>
</html>